1. Field of the Invention
The present disclosure relates to a method for producing a semiconductor light emitting element, and more particularly to a method for producing a semiconductor light emitting element by dividing a wafer into chips by irradiating the inside of the wafer with laser beam.
2. Description of the Related Art
Semiconductor light emitting elements can be small and highly effective in power consumption, and can emit vivid color light. In addition, in the case of light emitting elements of semiconductor elements, there are no concerns about bulb burnout and the like. In addition, semiconductor light emitting elements have features such as excellent initial driving characteristics, resistance to vibration or ON/OFF repeats. Since semiconductor light emitting elements have these excellent features, semiconductor light emitting elements such as light emitting diode (hereinafter, occasionally referred to as “LED”) and laser diode (hereinafter, occasionally referred to as “LD”) have been used as various types of light sources. In particular, in recent years, light emitting diodes receive attention as light source for lighting replacement of fluorescent lamps, in other words, as next-generation lighting having long life and low power consumption. From this viewpoint, further improvement is required in light output and light emission efficiency.
Such a semiconductor light emitting element is produced by dividing a sapphire substrate with semiconductor layers into chips after the semiconductor layers are epitaxially grown on the sapphire substrate. In the known techniques, the wafer of the substrate and the semiconductor layers, which are stacked on the substrate, is divided into chips by a dicer, a scriber, a laser scriber, or the like. In the case where nitride semiconductors are used for the semiconductor layers, sapphire substrates are typically used as the growth substrate.
Methods for dividing a wafer including a sapphire substrate have been proposed which irradiate the wafer with laser beam from the back surface side of the sapphire substrate using a femtosecond pulse laser so that altered areas are produced inside the sapphire substrate whereby producing division grooves or cracks from extending from the altered areas. See Japanese Patent Laid-Open Publication Nos. JP 2006-245,043 A, and 2008-98,465 A, for example.
However, it is relatively difficult to extend cracks in some substrates, and requires waiting time from the irradiation of laser beam to the extension of cracks. If the waiting time is long, the cycle time for producing the semiconductor light emitting element becomes long. As a result, the production efficiency becomes low.
The present invention is devised in light of the disadvantageous features as described above. It is one object of the present invention to provide a method for producing a semiconductor light emitting element capable of facilitating extension of cracks.